1. Field of the Invention
The present invention relates to a nozzle for spraying sublimable solid particles entrained in gas, such as CO2 snow or Ar snow, onto a surface of an object to be cleaned, and more particularly, to a nozzle for spraying sublimable solid particles capable of preventing frost from forming at surfaces of the nozzle and the object due to ultra-low temperature snow.
2. Description of the Related Art
As is well known, fine contaminant particles can be removed from a surface of an object to be cleaned, such as a semiconductor wafer or an LCD (liquid crystal display) substrate, using CO2 mixed with solid particles and gases—so-called CO2 snow—without damaging the surface of the object.
The CO2 snow passes through a venturi formed in a nozzle to generate solid particles which then grow and are sprayed onto the surface of the object to remove fine contaminant particles using impact energy of the solid particles colliding with the object. The impact energy of the CO2 snow may be increased by accelerating the CO2 snow using inert gas such as N2 (generally, referred to as carrier gas). CO2 snow that has removed contaminants by colliding with the surface of the object can be directly sublimated so as to leave no residue on the surface of the object. This cleaning method may be performed using sublimable solid particles such as Ar, and so on, for the substitution of CO2.
However, since the cleaning method using the CO2 snow is performed at a very low temperature of not more than −60° C., moisture in the air may condense on the surfaces of the nozzle and the object to generate frost. When frost is generated, contaminants in the air may attach to a surface of the substrate to seriously damage the semiconductor wafer or the LCD substrate, which requires a very fine cleaning process.
Therefore, typically, it is possible to prevent frost by receiving the nozzle and the object in a sealed chamber and maintaining the chamber at high temperature and low humidity. In this case, since static electricity may be generated in a dry environment and cause contaminant particles separated from the surface of the object to be reattached to the surface of the object, a separate device for preventing static electricity is required, which places a restriction on the cleaning environment and requires a plurality of auxiliary members.